Ultrix' /etc/crontab as a time-bomb [short joke].

From: Pete Turnbull <pete_at_dunnington.u-net.com>
Date: Thu Mar 21 02:07:59 2002

On Mar 20, 18:05, Gunther Schadow wrote:
> Hihi, our little training in risk-assessment tonight is the following
> sippet of a crontab entry, scheduled to run dayly around midnight:
> (cd /usr/preserve ; find . -mtime +7 -a -exec rm -f {} \;)
> why is this a bad idea and what happened to me last night as I was
> playing with my VAX6460?

Because Bad Things happen if the cd fails...

> Answer: the /usr/preserve was a symlink to /usr/var/preserve which
> didn't exist. What happened next?

> All files that were not accessed for more than 7 days were being deleted

The correct way to do someting like this in a cron entry is to check the
return code from the cd command, and only execute the rest of the command
if the cd succeeds, eg

 (cd /usr/preserve && find . -mtime +7 -a -exec rm -f {} \;)

Pete						Peter Turnbull
						Network Manager
						University of York
Received on Thu Mar 21 2002 - 02:07:59 GMT

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